In today's world, vehicles, computers, and other access-controlled devices are increasingly making use of radio transmitting security tokens, such as key fobs, smart phones, and other user identification devices, to detect the presence of an authorized user. For example, when a user of a security enabled device requests access to the device, the secured device looks for the presence of a security token. To facilitate an authentication process, the secured device may send a radio signal requesting that the security token transmit an authentication key, which the secured device can use to verify whether the user (i.e., operator) seeking access is entitled to the requested access.
More recently, it has been recognized that it would be advantageous for devices to detect when an authorized user is approaching. This ability to detect an approaching user can be useful for activating one or more welcoming features such as lighting or the playing of an audible greeting. To facilitate the detection of an approaching security token, a security enabled device (i.e., a host device) may periodically transmit a wake-up signal configured to be received by a security token (e.g., a key fob or a smart phone). Upon receipt of a wake-up message from the host device, the security token transmits a response configured to be received by the host device. Upon hearing the response from the security token, the host device may conclude that the security token is approaching and initiate welcoming features.
To improve the detection of an approaching security token, the host device may decrease the period of time between wake-up transmissions. For example, one contemplated system sends four wake-up messages per second or one wake-up message every 250 ms. Since the host device may be equipped with a large rechargeable source of power, the repeated transmissions do not typically cause that power supply to become depleted. Security tokens such as key fobs and smart phones, however, typically have a much more limited supply of stored power. Therefore, where a security token is situated so as to receive a large number of wake-up messages and transmit a correspondingly large number of responses, such as where the security token has been left in close proximity to the host device for an extended period of time, the power supply in the security token may become depleted in an unreasonably short period of time, leading to failure of the approach detection features and dissatisfaction of the operator.
Thus, in addition to the ability to detect an approaching security token, it is also important for the vehicle to be able to distinguish a newly approaching security token from a security token that may have remained in or near the vehicle for some period of time. This ability to distinguish a new approach from a recurring presence can be important not only so that the welcome functions are not activated at inappropriate times, but also to prevent overconsumption of battery life in the security token.
Accordingly, it is desirable to provide a system and method for detecting the presence of a user identification device, wherein an approach detection function may be selectively and independently disabled, enabled and/or personalized for each individual UID assigned to the vehicle.